Conduit system for conveying fibrous stock from deaerator chamber to headbox in papermaking machine

ABSTRACT

Papermaking apparatus in which deaerated papermaking stock is gravity fed from the evacuated chamber of a stock receiver to paper web-forming means through dropleg supply conduit system interconnecting the bottom of this chamber and the exit slot or slice of paper web-forming headbox, the dropleg conduit system having entry communication with the receiver chamber along a substantial part of a major lateral expanse of the bottom portion of the deaerated stock collecting zone thereof, the droplet conduit system preferably having exit communication with the delivery passage of the paper web-forming headbox transversely in the direction of the transverse length of the exit slice. The conduit system is provided such that its flow course between the stock receiver and the web-forming headbox delivery passage has no course deviation laterally of the web-forming means axis. The dropleg conduit system may be provided in the form of a plurality of closely spaced parallel arranged pipes, the entry ends thereof being connected to the chamber collecting zone and the exit ends thereof being connected to the delivery passage. The dropleg conduit system also may be provided as a single, relatively wide chute having its passage connected by an elongated slot extending along a substantial portion of a major lateral expanse of the bottom of the chamber collecting zone. Various forms of flow control valves may be embodied in the dropleg supply conduit system to restrict selectively their effective size for correspondingly regulating the rate of flow of the deaerated stock to the paper web-forming headbox in accordance with the demand for the particular grade of paper being made.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of .[.pending.]. applicationSer. No. 813,646 filed Apr. 4, 1969, now abandoned.

BACKGROUND OF THE INVENTION

The present invention relates to improvements in papermaking systems andparticularly the apparatus employed therein for transferring deaeratedpapermaking stock from a collecting zone of an evacuated chamber definedby a stock receiver to the paper web-forming means.

Modern methods of papermaking often take advantage of the benefits ofemploying deaerated papermaking stock suspension as the furnish to theheadbox of the papermaking machine or other point of use. Deaeration maybe accomplished by atomizing the stock suspension into an enclosedreceiver which is maintained under deaerating vacuum. The stock may alsobe cleaned in centrifugal solids separating means, such as hydrocyclonesor other forms of cleaners, and such separating means may advantageouslybe combined with the deaeration means whereby the dirt-poor or acceptsfraction from the separating means is sprayed directly into theevacuated receiver. Plural stages of cleaning may be employed and theaccepts fraction from all or some of the cleaning stages subsequent tothe primary stage may similarly be deaerated. A more completedescription of method and apparatus for deaerating and for cleaning maybe found in U.S. Pats. 1,853,849, 2,571,219, 2,614,656, 2,642,950,2,685,937, 2,717,536, 2,751,031, 2,876,860, 2,931,503, 3,131,117,3,206,917, Kaiser U.S. Ser. No. 417,161 filed Dec. 9, 1964, now U.S.Pat. 3,432,036, Kaiser U.S. Ser. No. 526,256 filed Feb. 9. 1966, nowabandoned, and Kaiser U.S. Ser. No. 694,494 filed Dec. 29, 1967, nowU.S. Pat. 3,538,680.

In papermaking systems employing deaerated papermaking stock, thedeaerated stock commonly is delivered from an evacuated stock receiverto the paper web-forming means by single relatively small supply conduitmeans and fan pump or like impeller means connecting the receiver withthe headbox of the web-forming means, as shown, e.g., in the Kaiser etal. U.S. Pat. 3,206,917. The supply conduit means are connected to thebottom portion of the collecting zone of the stock receiver at a centrallocation, and the communicating outlet from this zone to the supplyconduit occupies but a very small fraction of the lateral expanse of thebottom portion of the collecting zone. At the outlet end of the supplyconduit, the papermaking stock is delivered to a manifold for supplyingthe stock to the headbox of the web-forming means, the manifoldextending laterally to both sides of the supply conduit in order toattempt to attain even distribution of the stock along the expanse ofthe slice in the headbox from whence issues the stream of effluentribbon of stock cast, for example, onto the traveling wire of aFourdrinier unit. The conveyance of stock from the stock receiver to theweb-forming means headbox in such type of conduit thus involvesundesirable alterations in the conduit flow course in a directionlaterally of the web-forming means axis particularly in effecting flowcourse transition from the conduit to outlet at the back of theweb-forming means headbox. Further, the passage of the deaerated stockfrom the receiver to the headbox in a relatively small artery whichdemands that there be a relatively high flow velocity that may requirerelatively high pump pressure in order to maintain the transfer flow ofa predetermined rate. Certain system operating problems may attend thismode of supplying deaerated stock to the web-forming means, includingfloccing or coagulation of stock fibers and like stock particles oninternal conduit surfaces such as valve closure members, elbows, etc.,as well as cavitation at points where flow pressure drops, such as atlocations wherein conduit passage size is diminished with concomitantincrease in velocity of flow, especially at the papermaker's valve.Cavitation-promoting conditions are desirably eliminated from the systemsince cavitation, especially at the papermaker's valve, can introduce amarked unevenness of flow to the web-forming means and adverse effectupon the quality and uniformity of paper formed on the wire or otherforming means. Also, the magnitude of the pressure drop often causesvibration and shaking of the papermaker's valve and associated parts ofthe system, which vibration also imparts non-uniformity to the productas well as causing wear and damage to the system structure.

Certain papermaking system improvements have been proposed to minimizethe above-described drawbacks in prior art papermaking systems. Forexample, Kaiser U.S. patent application Ser. No. 526,256, filed Feb. 9,1966, now abandoned, discloses an improved papermaking system whereinthe transfer of papermaking stock from the stock receiver to the headboxof the paper web-forming means is effected by gravity, thus eliminatingthe need for the conventional stock transfer pump with consequenteffective reduction of cavitation as a system shortcoming as well asimprovement in flow conditions to and at the paper web-forming means.The desirable end of reducing cavitation as well as improving theconsistency and quality of furnish supplied to the web-forming meanswith the provision of a greater degree of constancy of pressure withinthe supply conduit is achieved by elevating the stock receiver a heightabove the delivery slot or slice of the web-forming means that providesa hydrostatic head between the elevation of the surface of the deaeratedpapermaking stock in the receiver and the elevation of the web-forminglevel of the paper forming means in excess of that necessary to offsetthe condition or degree of vacuum within the stock receiver deaeratingchamber plus all of the intervening hydraulic losses associated with thesupply conduit, papermaker's valve, etc., the overall vertical distancebetween these two elevations being measured in terms of a dropleg ofcertain height.

SUMMARY OF THE INVENTION

The present invention is concerned generally with improvements inpapermaking systems and specifically with improvements in the supplyconduit means by which deaerated papermaking stock is transferred fromthe collecting zone of an evacuated stock receiver chamber wherein thestock may suitably have been deaerated, to the paper web-forming means.It is a feature of the invention that the supply conduit means connectedwith the stock receiver in air-excluding relationship have entry theretoin communication with the chamber defined by the stock receiver, andparticularly a stock collecting zone thereof along a substantial portionof a major lateral expanse of the collecting zone bottom portion, withexit flow from the supply conduit means preferably being provided alonga relatively wide course extending transversely of the delivery passageof the web-forming means, such as a headbox structure thereof. In thismanner most direct transfer of the papermaking stock between theindicated entrance and exit locations is achieved, with the transferbeing effected by elevating the stock receiver a sufficient distanceabove the web-forming level to eliminate the need for a pump unit.

By withdrawing the deaerated stock from the receiver chamber collectingzone along a substantial portion of a major lateral expanse of thebottom thereof there is obtained a desirable degree of uniformity ofsuspension of the fibrous solids in the deaerated supply stock fed tothe web-forming means by the present improved dropleg supply conduitmeans. The present demand of an increase in the rate of production ofthe paper requires papermaking apparatus of larger capacity to providethe necessary increase in the rate of flow of deaerated stock suppliedto the speeded-up web-forming means. Since certain problems imposelimitations upon provisions for increasing the flow velocity of thesupplied stock through supply conduits of prior design, the greatercapacity of embodiments of the present dropleg supply conduit means isan important advantage realized by the use thereof. Providing largecapacity flow courses for the supplied stock by certain forms of thepresent invention also permits flow to the exit slice through thedelivery passage leading thereto with minimum tendency to createundesired turbulence. Where the delivery passage to the web-formingmeans is a headbox structure, the present invention provides for moreuniform introduction of stock transversely across the back expanse ofthe headbox. This is not always possible when prior art conduit meansare employed and deliver stock to a central location at first entry tothe headbox from whence it must be conveyed laterally within manifoldmeans for distribution across the expanse of the headbox. Moreover,uniform introduction and distribution with prior art conduit means isparticularly difficult to achieve where the flow rate is varied over awide range of values.

Advantages of the improvement of the present invention may be realizedby providing the supply conduit means in a form comprising a pluralityor bank of separate dropleg pipes having their upper ends connected inair-excluding manner to the bottom of the receiver which defines thebottom portion of the collecting zone of the interior evacuated chamberfor communication to the collecting zone, and in a pattern ofdistribution that arranges them along a substantial portion of a majorlateral expanse of the bottom of this zone, such conduit means beingcharacterized further by the feature that the flow course providedthereby does not undergo between entry thereto and exit therefrom, anycourse alteration in a direction laterally of the axis of theweb-forming means, i.e., the papermaking machine axis. In the event thatthe collecting zone is in the form of an elongated or longitudinal,lateral or substantially horizontal and generally cylindrical receiverchamber, or a transverse section thereof, its bottom portion may be inthe form of an elongated trough, and such pattern of distribution ofcommunications to the passages of the bank of pipes may be in a closelyspaced array extending longitudinally of the trough, the pipes beingarranged parallel with each other. This bottom portion may include anelongated, rectangular well or recess intervening the top ends of thedropleg supply pipes and the major cylindrical area of the chamber withthe space therein forming a lower section of the chamber bottom portion.The communications of the supply pipe passages to the chamber collectingzone, or such a well thereof, may also be arranged along sinuous orzig-zag lines, or in parallel rows to attain the desired expanse ofdistribution. If the section of the evacuated receiver chamber whichconstitutes the collecting zone is substantially square or rectangularin plan view the communications of the supply pipe passages thereto, orto a well section thereof, may be arranged in a variety of patterns atany convenient location below the level of stock therein, such as alongone or both diagonals of the square, or in rows, or along margins ofprogressively smaller squares with inner ones thereof enclosed in outerones, or in random arrangement. In the event that the receiver standsupright the lower end section may constitute the collecting zone and thepattern of distribution of the communicating openings may bediametrical, or radial, or arranged in coaxial circles, etc., in theevent that the transverse section of the receiver is generally circular,the flow course provided by the supply pipe passages being as indicatedsuch that there is no flow course deviation therein laterally of thepapermaking machine axis. It will thus be seen that a large variety ofpatterns of distribution of the communicating openings which connect thepassages of the dropleg supply conduit pipes to the evacuated collectingzone will satisfy the requirement of arrangement along a substantialportion of a major lateral expanse of the bottom of this zone.

The lower exit ends of such a plurality or bank of supply conduit pipeshave their passages connected in air-excluding manner to a deliverypassage leading to the web-forming means exit slot or slice. Thisdelivery passage may be defined by a suitable transition sleeve, whichmay be rectangular in transverse section, or it may be in the form of asection of the interior of a suitable headbox, and the like. While itmay be preferred that the exit openings of the lower ends of the droplegsupply pipes be arranged in an aligned array directed toward the exitslice, such as by means of a curved transition sleeve defining theintervening delivery passage, with the length of such array approachingthe transverse length of the slice, it is to be understood that suchlower exit ends may be clustered together with, for example, theclustered ends connected to the top of the chamber of suitable headboxstructure, in which case suitable provision will be made to avoiddevelopment within the headbox chamber of an undesirable degree ofturbulence.

According to the present invention, the dropleg supply conduit meansalso may be provided as a single, relatively wide, dropleg chute, suchas one of rectangular cross-section or other appropriate configuration,having its top end connected in air-excluding manner to the bottom ofthe receiver for communication to the collecting zone of the entry endof its flow course or passage through the bottom of the receiver by anelongated slot which extends along a substantial part of a major lateralexpanse of the collecting zone bottom portion. The lower exit end ofthis chute is connected in air-excluding manner to the means definingthe delivery passage which leads to the exit slot or slice, preferablywith the exit end of the chute passage being arranged with itstransverse width extending in the direction of or substantially parallelto the transverse length of the exit slice and communicating herewith. Alower end section of the chute may be shaped to serve as a transitionstructure for defining the delivery passage for smoothly turning thedirection of flow from a downward direction to a lateral path for directfeed to the exit slice. In a preferred embodiment, the dropleg chute hasuniform width from its entry to its exit ends, such width furtherpreferably being equal to the width of the outlet slice of the headboxat the web-forming means.

While it may be preferred to orient or suspend the dropleg supply chutesubstantially vertically it is to be understood that it may extendobliquely down from connection to the receiver bottom, such as along aline which is offset a minor transverse distance from a vertical planethrough the receiver axis, to approach at an acute angle the lateralplane of exit flow from the slice, thereby reducing the required degreeof turning of the flow through the delivery passage. If desired, theconnection of the receiver bottom to the top of the oblique chute may beeffected substantially in the vertical axial plane of the receiverthrough a smoothly curved transition section.

The supply conduit means provided by the present invention also may beused with the deaerating chambers disclosed in U.S. Pat. 3,538,680 forconveying stock from such deaerating chambers to the paper web-formingmeans. The conduit means can, for example, comprise a plurality ofparallel spaced pipes having entry connection thereto at the deaeratingchambers and outlet at the back of the paper web-forming means headbox.

Suitable flow regulating means, functioning as the papermaker's valve,may be associated with or provided in the supply conduit means, and itmay be in the form of a plurality of separate valves each associatedwith one of the separate pipes in the case where the supply conduitmeans comprises a plurality or bank of separate .[.dopleg.]..Iadd.dropleg .Iaddend.pipes, and as a single flow regulating device orcontrol valve in a system utilizing a single enlarged dropleg chute. Inaccordance with the invention, the specific forms of flow regulating orcontrol valve means can vary and can include butterfly-type valvesseparately located in the dropleg pipes, either interconnected tooperate together in tandem or ganged unison or with these valves beingindividually operated by suitable means. The purpose of the flowregulating means is to vary the rate of flow of deaerated stock to thepaper web-forming means, which may be attained either by altering thesize of the supply conduit means passage at some desired point, such asby suitable adjustable valve means, or by diverting some of the flowthrough this passage to recycle or to another point of use for reducingthe rate of delivery of deaerated stock to the web-forming means. Thusthe valving function or adjustment of the degree of flow blocking actionmay be performed by any suitable means of establishing a barrier ofvariable area of confrontation to flow in the dropleg supply conduitmeans, to serve as a papermaker's valve.

For example, the dropleg supply conduit, or each separate pipe of thedropleg bank of pipes, may include a tubular section in which is mountedan elongated, inflatable, elastic sleeve sealed at its opposite end tolongitudinally-spaced portions of the inner surface or wall of thetubular section so as to define an intervening circumscribing or annularchamber between the elastic sleeve and the tubular section intermediatethe sealed ends of the sleeve, with the interior of the sleeve servingas the through flow passage. By introducing a pressurized fluid into theannular chamber intervening the tubular section and the elastic sleevethe latter may be distended, i.e., bulged inwardly intermediate itssealed ends, for decreasing the available flow area of its interiorpassage through which the deaerated papermaking stock can pass. Thisaction constitutes a pinching of the through flow passage. Such pinchvalve is opened up by withdrawing or venting pressurized fluid from thechamber thereof.

In a system where a single chute is employed as supply conduit means, aspecial form of valve means preferably is provided. Such valve meanspreferably includes an elongated, selectively expandable andcontractable bladder arranged within the conduit passage transversely ofthe direction of flow therethrough, which may be in the form of anopen-ended sleeve that is transversely distortable in shape and havingits end in unconstrained, conformable and sliding abutment with theinner side surfaces of opposed walls of the conduit. A feed pipe mayextend through one or more walls of the conduit to the interior of orthrough the bladder for connecting the interior of the bladder throughone or more vents in the feed pipe with a source of fluid underpressure. The introduction and withdrawal of pressurized fluid to thebladder selectively varies the area of confrontation of the barrier thebladder offers to flow in the conduit, i.e., its flow blocking action,thereby selectively regulating stock flow through the conduit.

The flow regulating means which is associated with the supply conduitmeans may be of a type which determines the rate of delivery from thelatter by diverting or bypassing therefrom a quantity of the otherwisenormal flow therethrough. For example, each conduit structure, such aseach dropleg supply pipe of the bank thereof which together serve as thesupply conduit means in one embodiment, may be equipped with such a flowdiverting device that includes a lower end section of the pipe. Thislower end section is of certain cross-sectional area to determine theunit capacity thereof. A feed conduit for supplying deaerated stock tothe delivery passage leading to the exit slot or slice has its passagecommunicated to the passage of the pipe lower end section through anopening of a cross-sectional area lesser than that of the passage of thepipe lower end section at a certain point or elevation. Therebelow, aflow diverting or bypass conduit that has a passage of lesser capacitythan that of the passage through the lower end pipe section has itspassage connected to the latter, and the feed conduit and bypasspassages constitute together the sole outlets from the lower end pipesection. Thus, some of the flow through the dropleg supply pipe will becaused to flow into the feed conduit and the rate of this latter flowwill be determined by the rate of flow permitted in the bypass conduit.The latter may be determined by the size of the opening which serves asthe entry end to the bypass conduit passage or by flow regulating meansassociated with the bypass conduit, such as an adjustable valve mountedin the latter. The bypass conduit may feed the flow diverted therebyeither to a return line connected directly to the means for introducingthe stock into the receiver chamber or to the white water collecting pitof the web-forming means, and this may be accomplished selectively bysuitable valving equipment.

DESCRIPTION OF THE DRAWINGS

Other objects of the invention will in part be obvious and will in partappear from the following detailed description taken in connection withthe accompanying drawings, wherein like numerals identify similar partsthroughout, and in which:

FIG. 1 is a schematic representation, with parts in section and brokenaway, of improved papermaking apparatus constructed in accordance withthe principles of the present invention.

FIG. 2 is a perspective view to larger scale, with parts broken away, ofa portion of the apparatus illustrated in FIG. 1, showing the manner inwhich a plurality of dropleg separate pipes together serve as the supplyconduit means by which gravity transfer of stock from the receiver meansto the web-forming means is effected, a portion of the receiverstructure being shown in phantom for purposes of clarity.

FIG. 3 is a partial elevational view of a lower portion of droplegsupply means similar to that shown in FIG. 2, and of associatedstructure, illustrating a flow diverting or bypass piping arrangement toserve as a flow regulating means with which the rate of stock feed tothe web-forming means can be varied.

FIG. 4 is a fragmentary elevational view of another papermaker's valvearrangement with which stock feed to the web-forming means can bevaried, the arrangement involving the use of distendable elastic sleeveswithin each supply pipe to vary the flow passage size.

FIG. 5 is a partial elevational view, with parts broken away and insection, of a variation of the flow regulating means illustrated in FIG.3 which may serve to regulate the rate of stock feed to the web-formingmeans.

FIG. 6 is a perspective view somewhat similar to FIG. 3, illustratingthe dropleg supply conduit means as an enlarged, relatively wide,rectangular chute for effecting gravity transfer of deaerated stock fromthe receiver means to the web-forming means, the supply conduit meansembodying an elongated, selectively expandable and contractable bladdertype valve means serving as the papermaker's flow control valve tocontrol stock feed to the web-forming means.

FIGS. 7 and 8 are fragmentary perspective views to larger scale of asection of the supply conduit means shown in FIG. 6 illustrating,respectively, the flow control means bladder in expanded and contractedconditions.

FIG. 9 is an enlarged transverse sectional detail of the valve meansbladder shown in FIGS. 7 and 8 in expanded condition.

FIG. 10 is a longitudinal vertical sectional view, with parts brokenaway, of the valve means shown in FIGS. 7 and 8.

FIG. 11 is a fragmentary sectional view of an end portion of the valvemeans bladder depicted in FIGS. 6, 7 and 8 showing the manner in which aresilient seal may be affixed thereto for conformably engaging with theinner wall surfaces of the supply conduit to prevent fluid transferbetween the interior of the conduit and that of the bladder.

FIG. 12 is a front elevational view of the apparatus shown in FIG. 2wherein a plurality of dropleg pipes are used for conveying stock fromthe receiver to the papermaking machine headbox, and as viewed from thedirection of the papermaking machine axis.

FIG. 13 is an end elevation looking from the right end of the apparatusdepicted in FIG. 12.

FIG. 14 is a plan view of apparatus similar to that shown in FIG. 6wherein a single chute conduit is used for conveying stock from thestock receiver to the papermaking machine, the chute conduit being thesame width as the papermaking machine headbox outlet slice and being ofsubstantially uniform width from entry to exit ends thereof.

FIG. 15 is a plan view depicting the use of a plurality of dropleg pipesemployed for conveying stock from a deaerating chamber of the typedisclosed in U.S. Pat. 3,538,680, to the headbox of a papermakingmachine.

FIG. 16 is a side elevational view of FIG. 15.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention is concerned with improvements in papermakingsystems and especially the manner and means employed in said systems foreffecting transfer of deaerated stock from the stock receiver as furnishto the paper web-forming means. The following description relates to asystem employing a Fourdrinier unit as the paper web-forming means,although it should be understood that the improvements of the presentinvention have broader utility including, but not .[.liimted.]..Iadd.limited .Iaddend.to, use in papermaking systems that employ otherpaper web-forming means, such as multiple wire units, cylindrical units,vertical forming machines and the like.

A system embodying the improvements of the present invention is depictedschematically in FIG. 1 and includes a papermaking stock receiver 10,suitably an elongated, hollow and securely closed structure of suitablesize and shape, which is described and illustrated herein, by way ofexample, as being of generally cylindrical shape. Other receiverconfigurations, including those shown in U.S. Pat. 3,538,680 may beemployed. The receiver structure 10 defines an enclosed chamber 12 intowhich is introduced liquid, papermaking fibers which are treated in thechamber to remove absorbed, adsorbed, entrained and dissolved air fromthe fibers and other constituents of the fibers and liquid, the lattercommonly being water. The chamber 12 or a collecting zone thereof mayalso serve to accumulate a body or pond 14 of the deaerated papermakingstock, the surface 15 of the pond of stock so accumulated beingmaintained in the chamber at an essentially constant predetermined level23 for an important purpose described later, by known means, preferablythe means described in the Kaiser et al. U.S. Pat. 3,206,917, includingthe transverse weir mounted in the lower portion of the receiver chamberthat is illustrated and described therein. The interior of stockreceiver 10, i.e., chamber 12, is connected by conduit or pipe means 16located at the top thereof with an evacuating means .[.(not shown).].for maintaining the chamber under a condition of vacuum sufficient todeaerate air-containing, aqueous papermaking stock introduced into thischamber.

Introduction of air-containing stock into the receiver 10 can be made asan adjunct of a cleaning procedure for which various cleaner devices ofknown construction can be employed, solids separating means in the formof hydrocyclones 18 and described in the Samson et al. U.S. Pat.2,377,524 being preferred. The air-containing stock is delivered bymeans of pump 20 through conduit 22 to inlet headers 24 to which thehydrocyclones 18 or other suitable .[.stock-introucing.]..Iadd.stock-introducing .Iaddend.means are connected, the system sourcesfrom which the air-containing stock is withdrawn including a stuff box 5or other suitable source of fresh thick stock. The air-containing stockmay be diluted prior to its delivery to the hydrocyclones 18 by admixingwhite water therewith, and the source of the white water suitably may bebody 8 thereof in wire pit 9 associated with the web-forming means 30,which may be drawn off through conduit 11 connected to the intake ofpump 20, and this conduit may also serve to supply stock from stuff box5 to this pump. The air-containing stock delivered to each hydrocyclone18 is separated therein in the manner described, e.g., in U.S. Pat.2,377,524 into a dirt-poor or accepts portion which exits thehydrocyclone through an inlet pipe 32, entering as an atomized sprayinto the receiver chamber 12, and a dirt-rich or rejects portiondischarged from the apex of each hydrocyclone to a rejects header 34from whence the rejects are passed to a point of further use in thesystem, the rejects header being maintained under evacuated condition.Reuse of the rejects, for example, may include returning them by meansof conduit 36 to a subsequent cleaning stage, e.g., in the mannerdisclosed in the Kaiser U.S. Pat. 3,432,036.

As will be noted, the hydrocyclones 18 and their exit pipes 32 can beconnected at the stock receiver in various arrangements as, for example,in two groups located symmetrically on opposite sides of the stockreceiver longitudinal axis, in the manner shown in FIG. 1. The acceptsentering the top portion of the chamber 12 are readily deaerated thereinsince the sprays of stock 37 impinge on the receiver inner surfacesabove the stock pond surface 15, as shown, causing it to break up,thereby facilitating deaeration. The sprayed stock then falls down toaccumulate in a collecting zone as the .[.pound.]. .Iadd.pond.Iaddend.14 in the manner shown, the level of the stock surface 15 beingmaintained at the elevation 23 as previously indicated. In connectionwith maintaining the stock surface level at elevation 23, the levelcontrol means employed for this purpose, such as weir 26 indicated inbroken lines at 26 in FIG. 2, functions to return overflow stock to thesuction side of pump 20 through dropleg conduit 27 since the stockreceiver is elevated a certain height above the pump 20 in the mannerdescribed in Kaiser U.S. Pat. 3,432,036.

The deaerated stock accumulated in the pond 14 within the receiverchamber 12 is then transferred by means of gravity through suitablesupply conduit means 50 provided in accordance with the presentinvention. One suitable arrangement of supply conduit means is thatshown in detail in FIG. 2, and is comprised of a plurality or bank ofseparate dropleg pipes 52-62, preferably similar and of uniform size. Asa preliminary to further specific description of the supply conduitmeans 50, a brief description of the employment of gravity as a transfermeans may here be given to advantage. Gravity transfer is achieved byelevating the stock receiver 10 a distance (H₁) above the web-forminglevel 41 of the paper web-forming means 30, i.e., at the outlet slice 39of its delivery passage or headbox 38, so that the supply conduit means50 connecting the bottom of the deaerating chamber 12 and the headbox ofthe Fourdrinier unit constitutes a dropleg of sufficient height toovercome the effect of vacuum on the outflow of stock from the receiverand to offset all equipment pressure drops in the supply system, andadditionally to provide the pressure or head of stock necessary for thedesired rate of transfer of treated stock or furnish to and out of theslice of the headbox and onto the traveling wire 40 of the web-formingmeans at a velocity essentially the same as that of traveling wire 40.The advantages attending the use of such a dropleg in a papermakingsystem as a stock transfer means in place of a fan pump employed in mostprior art systems include reduction of cavitation at the papermaker'svalve, greater system flexibility and more consistent quality anduniformity of paper formed by the system, an improved system embodyingsuch dropleg means being described in the identified U.S. patentapplication Ser. No. 526,256 of Feb. 9. 1966, now abandoned. .Iadd.Ifdesired and with reference to FIG. 1, a portion of the deaerated stockbeing delivered to the paper web-forming means can be bypassed throughvalve 42 and conduit 43 to the intake side of pump 20. .Iaddend.

Turning now to a consideration of the improved supply conduit meansprovided by the present invention, reference is again made to FIG. 2 ofthe drawings wherein it will be noted that the system stock receiver 10is depicted, by way of example, as being of elongated cylindrical shapewith its major axis disposed horizontally, although it should beunderstood that the stock receiver could have its major axis disposedvertically or at any angle from horizontal to vertical and it could haveother shapes including elliptical, etc. The solids separating means orhydrocyclones 18 shown in FIG. 1 are not illustrated in FIG. 2 in orderthat the construction and manner in which the supply conduit means 50 isarranged can be shown with enhanced clarity, the employment of suchseparating means being optional although preferred. As mentioned above,the supply conduit means 50 is comprised of a plurality or bank ofseparate dropleg pipes 52-62 which depend in generally verticaldisposition and have their open upper or entry ends 63 secured inair-excluding relationship to the bottom of the stock receiver 10 belowthe level of the pond therein, the pipes, for example, being arrangedsuch that their entry ends are closely spaced with respect to each otherin an array extending horizontally and longitudinally of the chamber 12or along a substantial part of a major lateral expanse of the bottom ofits collecting zone, thereby providing that entry communication of thesepipes with the chamber collecting zone bottom portion is attainedthroughout a major part thereof. Thus the deaerated stock which isresident in pond 14 thereof is readily accessible to the entry ends ofthe pipes 52-62 below the level of the pond. It will be understood thatthe inlet pipes 32 well disperse the stock within the collecting zone ofthe chamber 12 to promote uniformity of the feed delivered to theweb-forming means 30, and their locations in this chamber facilitatesminimizing the exit course from the receiver 10. Hence entrycommunication to the supply conduit means occurs with but minimumlateral displacement of the papermaking stock from point of first entryto the ponding area of the chamber and the point at which it leaves whenentering the pipes 52-62. The dropleg pipes 52-62 are preferably, butnot necessarily, located directly below and in alignment with thecentral axis of the stock receiver. Thus, with this preferredarrangement of the droplet pipes 52-62, the hydrocyclones 18 arearranged at locations on each side of the receiver axis spaced therefromin order to assure that a maximum number of these supply conduit pipescan be connected with the bottom of the receiver 10 without interferenceby the inlet pipes 32 of the hydrocyclones. The lower or outlet ends ofthe dropleg pipes 52-62 are connected in air-excluding relationship withthe delivery passage or headbox of the web-forming means. The headbox 38is intended to be of conventional construction, but it may include asweeping transition piece 68 which is used to convey the deaerated stockto the slice 39 of the headbox from which it passes as a relatively widestream or jet of stock onto the traveling wire 40 of the Fourdrinierunit, the plane of stock flow thereby being changed from essentiallyvertical to substantially horizontal. Such transition piece of courseneed not .[.to.]. .Iadd.be .Iaddend.provided if the traveling wire orweb-forming means traverses a vertically disposed web-forming path inwhich event the plane of the stock flow will be correspondingly avertical one. Also it will be understood that if such web-forming pathshould traverse a plane intermediate the usual horizontal and verticalpaths as are known, the transition piece would be modified accordinglyto effect the change in flow path of the stock from the vertical to theweb-forming path plane. The connection of the lower ends of the droplegpipes 52-62 with the transition piece 68 is characterized by their lowerexit ends being arranged in a closely spaced array extendingtransversely of the headbox 38.

As indicated earlier, the dropleg pipes 52-62 are adapted to convey thedeaerated papermaking stock or furnish to the paper web-forming meansunder the influence of a dropleg in lieu of utilization of a fan-typepump in the conventional manner. For that purpose the dropleg pipes52-62 are of sufficient height to enable location of the head of stockin the receiver 10 at an elevation (H₁), i.e., the vertical distancemeasured between the level 23 of the surface 15 of the stock accumulatedin the collecting zone of the receiver chamber 12, as the pond 14thereof, and the web-forming level 41 of the paper web-forming means 30.The height (H₁) is such as to provide a hydrostatic head sufficient toovercome the evacuated condition within the receiver chamber 12, plusthat which will compensate for the hydraulic losses occurring in thedropleg pipes 52-62, the papermaker's valve means .[.64,.]. .Iadd.164,.Iaddend.the headbox transition piece 68, and any other cause forhydraulic head loss. In a practical system installation, this height(H₁) can generally vary over a fairly wide range of heights, dependingon the type of paper being made as well as the type of equipment withwhich the paper web is formed, as for example, certain cylindricalweb-forming units require no effluent jet velocity, so hydrostaticcompensation for this factor need not be provided.

The dropleg supply pipes 52-62 shown in FIG. 2 may be fitted withpapermaker's valve means 164 of conventional construction, each beingseparately equipped with a butterfly-type of valve 164. These valves 164can be individually controlled, or they may be operated in tandem byganging them and providing a known type of actuating device 65 forvarying the butterfly setting, the actuating device being controlledwith a suitable controller indicated at 66. As previously indicated, achange in the grade of paper being made with the system is provided mostreadily by altering the flow rate of stock to the headbox 38. this isconventionally done, and as will be discerned with reference to FIG. 1,by changing the degree of closure of the papermaker's valve means.[.64.]. .Iadd.164 .Iaddend.in the supply dropleg conduit means 50.

The present invention also provides improved forms of flow regulatingmeans for use in conjunction with the improved supply conduit means 50previously described. One form of improved flow regulating means isshown in FIG. 3, and it comprises a plurality of devices with each onethereof embodied in each of the separate dropleg pipes 52-62 shown inFIG. 2, each being substituted, for example, for one of thebutterfly-type valves 164. The flow regulating procedure associated withthis form of arrangement does not require physically positioning suchflow regulating means within each of the dropleg pipes 52-62 therebyallowing uninterrupted flow through each pipe. Instead, it involvesaltering the flow rate by bypassing or diverting a portion of thepapermaking stock feed or furnish flowing through each dropleg supplypipe 52-62 to a suitable point, such as the wire pit 8 wherein iscollected the white water drawn from the Fourdrinier unit 30 during theweb-forming operation .Iadd.stock being introduced through conduit 29connected to the intake side of pump 20.Iaddend.. For this purpose thelower end of each dropleg pipe 52-62 is terminated at a point short ofthe headbox 38 and, as is illustrated in FIG. 3 with respect to droplegpipe 52 by way of example, this lower end is connected with the headboxby means of the lateral leg of a smaller diameter tubular elbow 70having the open top end section 71 of its upright leg extending upthrough the closed bottom end of the dropleg pipe to an elevated point,as shown. A bypass or flow diversion tube 72 is communicated to theinterior of this dropleg pipe (such as 52) at a location appreciablybelow the open top of the upright leg 71 of tubular elbow 70. The flowdiversion tube 72 is connected through a valve 73 with a conduit 74which in turn can selectively discharge to either the wire pit 9 throughvalved pipe 75, or through valved conduit 77 to the suction side of pump20, depending on the settings of valves 76 and 78. The degree of closureof control valve 73 in the diversion tube 72 determines the rate ofdiverted flow through the latter either to the wire pit 9 or pump 20,and hence the rate of flow through the tubular elbow 70 connected withthe headbox 38. A particular advantage of this arrangement is that itcreates a mild turbulence in the lower end sections of the dropleg pipes52-62 which enhances dispersion of fibers in the system at thoselocations. Further, it maintains nearly uniform flow velocity in thedropleg pipes with varying flow rates as demanded in elbow 70 bydiverting unwanted or differences in flow through tube 72.

The principles of operation of the flow regulating means illustrated inFIG. 3 may be embodied in a simplified form which does not requireinsertion of an upper end section 71 of the feed conduit 70 appreciablyinto the interior of the closed bottom end of the dropleg supply pipe.As is illustrated in FIG. 5 the interior of the headbox 138 may beconnected by a feed conduit 270 by communicating the passsage of thisfeed conduit through the side wall of the lower end section 53 of thedropleg pipe 52 at an elevated point, such as that similar to theelevation of the open top end of the inserted section 71 of the feedconduit 70. The flow diverting bypass conduit 172 may then be connecteddirectly to the closed bottom end of the bottom end section 53 of thedropleg pipe for communicating the passage of this bypass conduit to thepassage of the bottom end section through an opening of lesser diameter.The resultant partial blocking of flow through the dropleg pipe as afraction thereof enters the bypass conduit 172 thus assures flow of afraction of the deaerated supply stock through the feed conduit 270toward the exit slice 39. The degree of diverted flow through the bypassconduit 172 is subject to adjustment by suitable valve means such asvalve 73. The diverted flow can be conveyed through conduit 74 to anysuitable point of use such as the Fourdrinier wire pit.

Another form of improved papermaker's valve means is in the form of aplurality of individual valves, each inserted in one of the droplegsupply pipes 52-62, one of which is illustrated by way of example inFIG. 4 at 264. Each such valve 264 includes a connector sleeve 80connecting the lower end of a particular one of the dropleg pipes 52-62,such as 52 there illustrated, to an elbow means 170 which communicateswith the interior of headbox 138. Within the connector sleeve 80 ofvalve 264 is mounted a generally cylindrically-shaped or tubular,distendible or elastic sleeve 82 having its upper and lower endsannularly sealed to the inner surfaces of the connector sleeve atlongitudinally spaced points to define between the intervening sectionsof these sleeves an annular chamber 84. A supply conduit, indicated inbroken lines at 85, may connect a suitable source of pressurized fluidto the annular chamber 84 through any suitable flow control valve 88through a controller 86, so as controllably to increase the capacity ofthis annular chamber with attendant adjusted constriction of the flowpassage 89 through the elastic sleeve 82. Such controlled supply ofpressurized fluid may be common to all of the valves 264, or individuallike sources may be respectively associated with these valves for all ofthe dropleg supply pipes 52-62. The resulting variations of the sizes ofthe flow passages 89 through valves 264 causes corresponding variationsin the stock flow rate through the dropleg pipe 52-62 to the headbox 138and resulting variations in the rate of delivery of the stock from theheadbox slice 39. A particular advantage of this form of valve 264 isthe ease with which each thereof is operated to control rate of flowthrough the respective dropleg pipes 52-62 to the headbox 138.

A preferred form or conduit means comprised of an arrangement of droplegpipes is depicted in FIGS. 12 and 13 of the drawings. Such apparatus isessentially the same as that earlier described in respect of FIG. 2 andincludes a stock receiver 410 provided with suitable connection means416 for evacuating the interior of the stock receiver as well as a levelcontrol in the form of a weir 426 for maintaining a pond 414 of stock inthe receiver. Stock from a primary cleaning stage is atomizingly sprayedinto the interior of the receiver through accepts pipes 432 in the samemanner as earlier in connection with the apparatus shown in FIGS. 1 and2. Certain constructional details of the apparatus have not been shownas the same are not necessary for complete understanding of the form ofconduit means. Stock receiver 410 also has an overflow compartment towhich stock overflowing weir 426 flows from whence stock is removedthrough dropleg conduit 427 and recycled to a cleaning stage. Thedroplet pipes 452-462 which connect the stock receiver 410 to theheadbox 438 of the web-forming means are arranged in a closely spacedarray extending longitudinally of the stock receiver and are parallelone with the others and parallel with the papermaking machine axis X-Y.In this manner, the dropleg pipes 452-462 provide flow courses forgravity transfer of stock from the receiver 410 to headbox 438 whichflow courses between the entry and exit ends thereof have no flow coursedeviation therein laterally of the axis X-Y of the papermaking machine,the axis X-Y of the papermaking machine lying in a vertical planepassing centrally longitudinally through the Fourdrinier wire 440. Inconsequence, stock can be conveyed from the stock receiver 410 to theweb-forming means 440 without any undesirable lateral displacement ofthe stock in respect of the machine axis thereby avoiding settlement offibers from the suspension as well as such other undesirable flowconditions which result from flow course alterations lateral to themachine axis and as are commonplace in prior art constructions. Thus,there is provided uniformity of stock flow through each of the pipes452-462, with consequential uniformity of distribution of stock flow outof the slice 439 of the headbox 438 onto the forming wire 440 withconcomitant enhanced uniformity of the quality of paper formed on thewire 440, particularly in high speed papermaking machines. Like theapparatus earlier described, each of the dropleg pipes 452-462 may beprovided with a papermaker's valve, as for example, the valve 442disposed in the dropleg pipe 462.

FIGS. 15 and 16 depict a further form of apparatus which utilizes adropleg conduit means according to the present invention for connectingthe papermaking stock source with the paper web-forming means, theparticular depicted embodiment being one employed in a system usingdeaerating chambers 512, 514, 516 in conjunction with a receiver 510 inthe manner disclosed in U.S. Pat. 3,538,680. A longitudinally disposedoverflow means such as a weir 517 extends along the length of thereceiver 510 and divides it into a first compartment 518 wherein a pondof stock is confined, which pond extends also into each of thedeaerating chambers. The second compartment 520 of the stock receiverprovides an overflow chamber into which overflows from the pond in thefirst compartment flows in conjunction with maintenance of a constantpond level in the chamber 518 at a certain distance above theweb-forming level of the papermaking machine. The second compartment 520also can be used as a deaerating space for deaerating stock from asecondary stage or subsequent cleaning operations, which stock can beadmitted to the receiver 510 through accepts pipes 522. Outflow from thecompartment 520 is effected by way of a suitable dropleg conduit 524through which stock is recycled to a cleaning stage. Conveyance of stockfrom each of the deaerating chambers 512-516 to the papermaking machineis effected by employment of a plurality of parallel spaced droplegpipes 552-570 which are connected at one end in air-excludingrelationship to the bottom of the deaerating chambers and at the otheror outlet end to the back of the headbox 538. As can be noted best fromFIG. 15, the closely spaced dropleg pipes 552-570 are arranged parallelwith each other and also parallel to the machine axis X-Y. Accordingly,the flow course provided by the dropleg pipes 552-570 has no coursedeviation therein extending laterally of the machine axis so that thestock issuing from slice 539 of the headbox 538 onto the wire 540 is ofoptimally uniform character both in respect of fiber distribution aswell as flow characteristics thereof.

In accordance with the present invention the dropleg supply conduitmeans communicating papermaking stock from the receiver chamber 12 tothe web-forming means 30 need not comprise a plurality of separatesupply pipes, such as 52-62 of FIG. 2, but instead may take the form ofa single, relatively wide, rectangularly-shaped conduit or chute 90,illustrated by way of example in FIG. 6. It will be noted that thesupply conduit or chute 90 has its upper or entry end 92 arranged withits major dimension extending a substantial distance along the length ofthe bottom of and connected in air-excluding relationship with the stockreceiver 10 for communicating the major portion of the lateral expanseof the collecting zone of chamber 12 to the interior of this chutethrough an elongated, longitudinally-extending slot in the receiverbottom wall. The length of this communicating slot may be substantiallyequal to the width of chute 90. The lower portion 94 of chute 90 ispreferably curved, as shown in FIG. 6, to provide a lateral outlet endsection 238 terminating in the wide, transverse, exit slot or slice 39,to define the delivery passage and thus serve as the equivalent of aheadbox of web-forming means 30 provided with such exit slice. Thecriteria indicated above with respect to the critical structural andoperational characteristics of the FIG. 2 embodiment are to be satisfiedby the modified form of FIG. 6. Thus the dimensions and sizes of theentrance end at 92 of the chute 90, and of cross-sections of the latterat various points between this entrance end and the exit slice 39 are tobe so related to the latter, and the height (H₁) of the dropleg conduitmeans provided by the chute is to be such as to assure attainment of thedesirable advantageous results indicated above.

FIG. 14 depicts a preferred form of chute embodiment, wherein the chute790 is substantially the same width as the web-forming means, that is,the same width as the outlet or slice 739 from whence stock issues outonto the papermaking machine wire 740. The entry 792 to the chute 790also is substantially the same width as slice 739 as is the chute at itspoint of connection to the back of the headbox 738 so that the stockconveyed through the chute does not undergo any flow course alterationlaterally of the machine axis X-Y. The apparatus of FIG. 14 includes astock receiver 710 and other features which are the same as thatdescribed earlier in connection with FIGS. 1, 2 and 6 with deaeratedstock being admitted to the receiver through accepts pipes 732 with thestock receiver being provided with an overflow 726 for the same purposeas described earlier.

The rate of flow through the supply chute 90 similarly is to be subjectto control and adjustment by suitable papermaker's valve means, and inselecting or designing such it should be recognized that the transversedimensions of this chute at a point convenient for mounting such valvemeans therein may be quite large. Thus papermaker's valves ofconventional construction which would perform the desired function couldbe quite massive both from the standpoint of size and of weight.Moreover, the time required for adjusting or substantially closing theflow passage through such conventional valves of massive size may bequite prolonged. An improved papermaker's valve 364 is thus proposed inFIGS. 6 to 11 inclusive for installation in chute 90. This valve 364includes a rectangular, hollow box frame 96 having top and bottomopenings margined by flange structure to anchor it in fluid-tight mannerto opposed sections of the chute 90. This valve frame defines thereinbetween its end panels 98 and side panels 100 a through passage chamber102 which constitutes a continuation of the flow passage through thechute 90. Within this passage chamber 102 is suitably mounted aselectively expandable and contractable bladder 104 formed of suitablematerial, such as light gauge sheet metal or flexible plastic, which canbe shaped as a tubular shell-like structure extending from end to end ofthe frame 96, i.e., side to side of the chute 90 in the manner indicatedin FIG. 10. As used herein, "tubular" is intended to be understood asincluding structure of an encircling cross-section without regard tospecific geometrical shapes. Thus circular, elliptical and squaresectional tubing are to be understood as being suited for use as thebladder 104 as well as other shapes. The end edges 106 of the tubularshell or bladder 104 are in unconstrained, conformable abutment with theinner surfaces 110 of the end panels 98 of the valve frame 96, and inorder to provide fluid-tight seals thereat these end edges may beequipped with elastic wiper rings 112, of rubber or other suitableelastic material, which may have wiping lips 114 in continuous slidingcontact with the inside surfaces 110. The tubular bladder 104 functionsto present a barrier of variable area of confrontation to the stock feedflow through the chute 90, which area can be altered according to thedegree to which the bladder is expanded transversely.

For admitting a pressurized fluid, such as air or suitable liquid, tothe chamber 116 within the bladder 104 selectively to expand the lattertransversely, a tubular supply conduit or feed pipe 118 extends tocommunication with this bladder chamber. Preferably the feed pipe 118extends interiorly through the bladder chamber 116, as is best seen inFIGS. 9 and 10, and passes through both of the frame and walls 98, influid-tight manner, to the exterior of these walls. The top side of feedpipe 118 preferably is secured to the top of the inner surface of thebladder 104 along a common longitudinal line 120, in any suitablemanner, such as by spot welding or brazing when these feed pipe andbladder are of such metallic materials as to be anchorable by suchmeans. The feed pipe 118 preferably is provided with a number of ventsor openings 122, which may be distributed along the bottom longitudinalzone thereof, as is indicated in FIGS. 9 and 10, so that pressurizedfluid fed into this pipe may be delivered into the bladder chamber 116for expanding the bladder 104 to a shape approaching cylindrical form,as indicated in FIG. 7. In such expanded condition the bladder 104provides appreciable blockage of the flow through the valve passagechamber 102, so as appreciably to constrict the flow passage within thechute 90. By releasing or withdrawing some of the pressurized fluid fromthe bladder chamber 116, the bladder 104 is permitted to collapselaterally toward the oval shape shown in FIG. 8, under the influence ofthe flow of stock or furnish through the valve passage chamber 102 whichforms a portion of the chute passage. The shape of the bladder 104depicted in FIG. 8 presents a lesser barrier to the flow of stockthrough the chute 90. Obviously, by varying the pressure of the fluidadmitted into the bladder 104, its shape can be altered between thoseshown in FIGS. 7 and 8 correspondingly to alter the rate of flow ofstock or furnish through this chute.

It may be desired to provide a plurality of longitudinally-spaced,transverse slots 124 extending through the top of the feed pipe 118 tocommunication with the bladder chamber 116, for bleed of air in thelatter into the feed pipe 118 for discharge when there is fluid flowthrough the latter to the exterior of the valve unit 364. The exteriorsupply end 126 of the pressurized fluid supply pipe may be equipped witha pressure regulator valve 128, and its exterior discharge end 130 maybe provided with a suitable flow control valve 132, which together willcontrol the degree of inflation of the bladder 104, and thus the rate ofstock or furnish flow through the chute 90. Preferably, the papermaker'svalve 364 will be located in the chute 90 a distance below the level 23of the surface of the pond 14 of deaerated stock in the collecting zoneof the receiver chamber 12 to prevent the existence of any vacuum withinthe conduit at the location of the valve.

It will thus be understood that in the plural-pipes embodiments of FIGS.2-5, 12, 13 and 15, and the chute embodiment of FIGS. 6-11 and 14, thesupply conduit means is of such construction and arrangement as to haveat its upper end entry communication to its through flow course, i.e.,its passage or passages as the case may be, from the collecting zone ofthe receiver chamber along a substantial portion of the major lateralexpanse of the bottom portion of the collecting zone. This supplyconduit means has exit communication from its flow course with theinterior of web-forming means. In any form of the latter there ispresent an interior delivery passage which terminates in or is providedwith a lateral exit slot or slice for delivery therefrom of a flat layeror effluent ribbon of the aqueous stock or furnish to be converted intoa paper web upon dewatering or removal of liquid therefrom, such asduring travel thereof on the traveling wire of a Fourdrinier unit. Insome types of such web-forming means the latter may include a headbox,conventionally identifiable as such, with its interior providing thedelivery passage leading to the exit slot or slice, but such usually ischaracterized by an enlarged interior chamber which receives thedeaerated supply stock that is then progressively expelled therefrom bythe imposed pressure through the exit slot or slice. However, theproduction of the desired paper web by apparatus of the presentinvention does not necessitate the use of an enlarged headbox chamber asthe delivery passage leading to the exit slot or slice since, as isindicated in FIG. 6, the lower end of such chute embodiment may providesuch delivery passage as a terminal section of the chute flow passage,as the full equivalent of the headbox chamber, for the purpose ofadvantageous use of the present invention. In either form the unique,dropleg supply conduit means of the present invention, either as aplurality or bank of spaced, dropleg pipes of the FIG. 2 embodiment orthe wide chute of the FIG. 6 embodiment which defines a single droplegpassage that is relatively narrow transverse of its width, has exitcommunication therefrom with a web-forming means delivery passage in atransversely-extending course opposite the major portion of thetransverse expanse of the exit slot or slice.

The term "collecting zone" as employed herein is broadly descriptive incharacter. For example, it is used as meaning at least a portion of theevacuated chamber of the receiver means into which aqueousair-containing papermaking stock is introduced in a manner thatfacilitates deaeration thereof to convert it to deaerated supply stockwhich is to be fed to a point of use, e.g., the paper web-forming meansof the papermaking apparatus. In some forms of the papermaking apparatusthis collecting zone may encompass the whole of the evacuated chamber,and in other forms thereof it may constitute only a portion thereof,with a remaining portion or portions thereof serving other purposes. Forexample, partition means may be provided in the evacuated chamber tosubdivide it into intercommunicated portions, with one serving as thecollecting zone source of accepts in a primary cleaning stage in theform of deaerated supply stock for feed to paper web-forming means,another serving as the collecting zone of a secondary cleaning stage fordeaerating cleaned rejects from the primary zone for return to thecollecting zone of the primary stage, and, if desired, still anotherserving as the collecting zone of a tertiary or subsequent cleaningstage for deaerating cleaned rejects from the secondary stage for returnto the collecting zone of the primary stage or other following stages.It is to be understood that the collecting zone of the primary stage ofany such papermaking apparatus does not necessarily provide anyappreciable residence of deaerated supply stock to accumulate or pondtherein before being withdrawn by the dropleg supply conduit means ofthe present invention for feed by the latter to the paper web-formingmeans, and such absence of ponding may characterize the operation oroperations in the evacuated chamber portion or portions serving as thecollecting zone or zones of the secondary and/or tertiary stages. Whenthere is no appreciable ponding in one or more of such evacuatedcollecting zones the surfaces of the deaerated aqueous stock that isdrawn off or received by droplet supply conduit means connecting theretomay find a level or levels in such supply conduit means below thereceiver means as determined by structural characteristics of suchsupply conduit means and parts of the apparatus which receive thedeaerated stock therefrom. Such partition means may comprise known formsof weir means which may dictate by their elevation the levels of thesurface of deaerated stock that may pond in such collecting zonesadjacent thereto when structural characteristics of the apparatus andthe rates of input and output to and from the receiver are such as todictate appreciable residence of the deaerated stock in the bottoms ofthese collecting zones, as taught in the identified prior U.S. Kaiser etal. Pat. 3,206,917 and U.S. Kaiser application Ser. No. 526,256, nowabandoned. Accordingly, a collecting zone of an evacuated chamberdefined by enclosing receiver means of papermaking apparatus embodyingfeatures of the present invention pertaining to dropleg supply conduitmeans may constitute the entire evacuated chamber, or only somestructurally delineated portion thereof, in which the deaerated supplystock is deposited for delivery to a point of use by such droplet supplyconduit means, whether this deposition develops some ponding in thecollecting zone or does not do so.

While the "collecting zone" above described has been discussed hereinwith respect to its being a space within an evacuated stock receiver, itwill be understood that the inventive concept of the novel droplegconduit means is not limited to use in conjunction with its entry endbeing connected with an evacuated receiver only. For example, a systemmay incorporate deaerating means separate from said receiver in whichcase the already deaerated stock will be delivered to the stock receiverfor conveyance therefrom through the dropleg conduit means to the paperweb-forming means. Consequently the stock receiver need not bemaintained under a condition of vacuum.

From the foregoing it will be discerned that the present inventionprovides important improvements in the papermaking art. The utilizationof dropleg conduit means for connecting the stock receiver with thepaper web-forming means results in achievement of even and uniformdistribution of fiber and water (uniform stock consistency) in the stockreceiver which character of uniform stock consistency is maintainedduring conveyance of the stock to and out of the paper web-forming meansslice. The fact that the flow course defined by the conduit means doesnot have any flow course deviation therein laterally of the papermakingmachine axis provides achievement of the aforementioned desirable endsand overcomes the problems of known forms of supply conduits which, forexample, produce unstable flow and distribution conditions when flowtherein is displaced laterally of the machine axis as vacuum, e.g., in across feed header. Furthermore, where a plurality of dropleg pipes areused as the conduit means, all such pipes are arranged in a flow courseparallel with the machine axis and where a single chute conduit is used,it is of uniform width from entry to exit thereof and symmetrical of themachine axis. Furthermore, the lateral expanse of the conduit means inrespect of the machine axis is substantially equal to the width of theslice of the papermaking machine headbox and the connection of theconduit means with the stock receiver in the collection shown thereof isalong an expanse of the same width substantially as the slice.Additionally, the conduit means of the present invention insures equaldistribution of flow across the back of the headbox inlet eliminatingthe need for recirculation through the headbox header to maintainuniform header pressures. Thus, the need for additional systemhorsepower expenditure and cleaners as most commonly required inconventional systems is eliminated.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are efficiently attained, and,since certain changes may be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

Having described my invention, what I claim as new and desire to secureby Letters Patent is the novel subject matter defined in the followingclaims:

What is claimed is:
 1. In papermaking apparatus comprisingpapermakingstock receiver means defining an enclosed evacuated chamber having acollecting zone for deaerated aqueous supply stock, and evacuating meansassociated with said chamber for maintaining its collecting zone under avacuum sufficient to deaerate aqueous papermaking stock introducedtherein, means for introducing aqueous papermaking stock into thecollecting zone of said chamber in a manner facilitating deaerationthereof to produce deaerated supply stock therein, a papermaking machineincluding a forming wire for converting deaerated supply stock into aweb of paper, and structure associated with said papermaking machinehaving an interior delivery passage provided with an exit slot fordelivery therefrom in the direction of the papermaking machine axis ofan effluent jet of stock onto said wire for conversion into a paper webupon removal of liquid therefrom, the improvement which comprisesdropleg supply conduit means defining a flow course communicating saidpapermaking machine associated structure delivery passage and its exitslot to a bottom portion of the evacuated chamber collecting zonethrough which deaerated supply stock can be conveyed from saidcollecting zone to said papermaking machine and comprising a pluralityof separate pipes, said pipes being parallel to each other and to saidmachine axis, said separate pipes each having a longitudinal throughflow passage with upper entry ends thereof being connected to saidcollecting zone bottom portion and arranged in closely spaced array withrespect to each other along a substantial part of a major lateralexpanse of said collecting zone bottom portion, lower exit ends of saidseparate pipes being connected with said papermaking machine associatedstructure delivery passage along a relatively wide course extendingtransversely of said delivery passage, and being arranged in closelyspaced array with respect to each other extending transversely in thedirection of the transverse length of said exit slot, the flow course ofsaid pipes between entry thereto and exit therefrom having no flowcourse deviation therein extending laterally of the axis of thepapermaking machine, said receiver means being elevated above said exitslot a sufficient height to overcome the effect of vacuum on gravityoutflow of stock from said receiver means, said distance of elevationbeing additionally such as to provide a stock pressure head sufficientto overcome flow frictional losses in said pipes and said papermakingmachine associated structure delivery passage and its exit slot, andflow control means associated with each of said pipes for regulating therate of flow of deaerated stock therethrough from said chambercollecting zone to said exit sot.
 2. The papermaking apparatus of claim1 wherein said flow control means comprises separate valves located ineach of said separate pipes.
 3. The papermaking apparatus of claim 2further comprising valve control means connected with each of saidseparate valves for operating them in ganged unison.
 4. The papermakingapparatus of claim 1.Iadd., .Iaddend.said flow control means being inthe form of a plurality of individual units each associated with one ofsaid pipes with each such unit comprising a lower end section of saidpipe of certain cross-sectional area and having a bottom end, a feedconduit intervening said exit slot and said lower end section andcommunicated to the interior of the latter at a point above its bottomend through an opening of lesser cross-sectional area, means defining aflow diverting bypass passage communicated to the interior of said lowerend section below the point of communication thereto of said feedconduit, and means limiting the rate of flow through said bypass passageto less than that through said bottom end section above said point ofcommunication thereto of said feed conduit which assures some flowthrough the latter.
 5. The papermaking apparatus of claim 4 wherein saidfeed conduit is a tubular member having an open-ended initial sectionsealed to the bottom end of said depending pipe lower end section andextending up into the interior of the latter to the point ofcommunication of the latter with said feed conduit whereby flow into thelatter from said depending pipe enters through the tubular member openend.
 6. The papermaking apparatus of claim 5 wherein said means limitingthe rate of flow through said bypass passage includes adjustable flowregulating means.
 7. .[. The papermaking apparatus of claim 1 whereinsaid dropleg supply conduit means comprises.]. .Iadd.In a papermakingapparatus comprisingpapermaking stock receiver means defining anenclosed evacuated chamber having a collecting zone for deaeratedaqueous supply stock, and evacuating means associated with said chamberfor maintaining its collecting zone under a vacuum sufficient todeaerate aqueous papermaking stock introduced therein, means forintroducing aqueous papermaking stock into the collecting zone of saidchamber in a manner facilitating deaeration thereof to produce deaeratedsupply stock therein, a papermaking machine including a forming wire forconverting deaerated supply stock into a web of paper, and structureassociated with said papermaking machine having an interior deliverypassage provided with an exit slot for delivery therefrom in thedirection of the papermaking machine axis of an effluent jet of stockonto said wire for conversion into a paper web upon removal of liquidtherefrom, the improvement which comprises dropleg supply conduit meansdefining a flow course communicating said papermaking machine associatedstructure delivery passage and its exit slot to a bottom portion of theevacuated chamber collecting zone through which deaerated supply stockcan be conveyed from said collecting zone to said papermaking machineand comprising .Iaddend.a depending and relatively wide chute ofrectangular cross-section having the entry end of its passage in theform of an elongated slot extending along a substantial portion of amajor lateral expanse of said collecting zone bottom portion andcommunicating therewith, the exit end of the passage of said chute beingarranged with its transverse width extending in the direction of thetransverse length of said exit slot and communicatingtherewith.[...]..Iadd., the flow course of said conduit means betweenentry thereto and exit therefrom having no flow course deviation thereinextending laterally of the axis of the papermaking machine, saidreceiver means being elevated above said exit slot a sufficient heightto overcome the effect of vacuum on gravity outflow of stock from saidreceiver means, said distance of elevation being additionally such as toprovide a stock pressure head sufficient to overcome flow frictionallosses in said supply conduit means flow course and said papermakingmachine associated structure delivery passage and its exit slot..Iaddend.
 8. The papermaking apparatus of claim 7 wherein said chute isof substantially uniform width between the entry and exit ends thereof.9. The papermaking apparatus of claim 7 wherein the web-forming path ofsaid papermaking machine wire is disposed horizontally, said exit slotbeing transversely coextensive with said path, said chute having anupper section which extends downwardly from said stock receiver and alower end transition section adapted to direct delivery flow ofdeaerated stock therefrom toward said exit slot.
 10. The papermakingapparatus of claim 7 wherein a fluid flow regulating valve is mountedtransversely within said chute passage and comprises a selectivelyexpandable and contractable hollow .[.body.]. .Iadd.bladder means.Iaddend.providing a barrier of variable area of confrontation crosswiseto fluid flow through said chute passage, means for supplyingpressurized fluid connected to said hollow .[.body,.]. .Iadd.bladdermeans, .Iaddend.and means to regulate admission and withdrawal of thepressurized fluid to the interiof of said hollow .[.valve body.]..Iadd.bladder means .Iaddend.for selectively expanding and contractingthe latter correspondingly to vary the effective flow blocking action ofsaid .[.valve body.]. .Iadd.bladder means.Iaddend. .
 11. The papermakingapparatus of claim 10 wherein said .[.hollow body.]. .Iadd.bladder means.Iaddend.is in the form of an elongated bladder having atransversely-extending chamber therein, said pressurized fluid supplymeans and flow regulating means including a tubular supply conduitextending in a fluid-tight manner through one wall of said chute towithin said bladder chamber and having an opening within this chambercommunicating said conduit with the latter.
 12. The papermakingapparatus of claim .[.10.]. .Iadd.11 .Iaddend.wherein outlet passagemeans having flow regulating means are provided which communicate saidbladder chamber to the exterior of said chute for controllably ventingthe latter.
 13. The papermaking apparatus of claim 12 wherein saidtubular supply conduit and said outlet passage means are provided assections of a continuous length of pipe extending through opposite sidesof said chute in fluid-tight manner to the exterior of the latter withone exterior section of this pipe serving as a portion of the supplyconduit and the other exterior section serving as a portion of theventing outlet passage means, and wherein the intermediate section ofsaid pipe extends through said bladder chamber and is provided with saidcommunicating opening located within the latter.
 14. The papermakingapparatus of claim 13 wherein said bladder is a radially flexibletubular shell having openings at opposite ends thereof each defined bysurrounding end edge means of said bladder tubular shell with these edgemeans being in unconstrained, conformable and fluid-tight wipingabutment to the adjacent inner surfaces of said opposite conduit sides.15. The papermaking apparatus of claim 14 wherein each of said end edgemeans includes an annular, flexible wiping lip slidably abutted to theopposed inner surface of the adjacent conduit side.
 16. The papermakingapparatus of claim 15 wherein said pipe is fixed to the interior surfaceof said bladder tubular shell along a common longitudinal line ofcontact therewith.
 17. The papermaking apparatus of claim 13 whereinsaid .[.hollow valve body constitutes a.]. bladder .Iadd.is .Iaddend.inthe form of a radially flexible tubular shell having openings atopposite ends thereof each defined by surrounding end edge means of saidbladder tubular shell with these edge means being in unconstrained,conformable and fluid-tight wiping abutment to said opposed inside facesof said conduit section.